1. Field
The present application relates to impedance matching. More particularly, the present application relates to a tunable impedance matching network.
2. Description of Related Art
In order to enable optimal power transfer between circuits having different impedance values, an impedance matching network is generally provided. If one or both of the impedance values being matched is subject to change, a tunable impedance matching network which can adjust for changing conditions is adopted.
Reference can be made, for example, to a cellular phone, which comprises RF (radio frequency) circuits and antennas. Impedance of an antenna of the cell phone can change as the environment surrounding the antenna changes, such as proximity of the antenna to metal, head, hand, and so forth. A tunable impedance matching network is tied to the antenna in order to compensate for such changes.
A tunable impedance matching network can also be used to compensate for tolerance in a product if the product requires specific design tolerances. The product may be automatically tuned in the factory during a test phase, producing a tuned setting of the tunable impedance matching network, so that the tunable impedance matching network is fixed at the tuned setting upon completion of the test phase.
A tunable impedance matching network may also be used to change filter performance or bandwidth in a product. For example, a variable impedance port of a tunable impedance matching network can be connected as a shunt (e.g. parallel) impedance in a filter. Adjusting impedance of the variable impedance port of the tunable impedance matching network can correspond to adjusting the shunt impedance of the filter, thereby changing filter performance.